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A survey was conducted to measure the extent of control of Littleseed canarygrass (Phalaris minor Retz.) in wheat crop in Ferozepur district in the state of Punjab (Trans-Gangetic Plains region) by Punjab Agricultural University Farmer Advisory Service Centre (FASC) Ferozepur during rabi 2018-19. The study aims to find out the causes of poor control of Phalaris minor in wheat crop on farm fields of farmers of Ferozepur district. 90 farm fields were selected randomly for collection of data. Survey data were analyzed using completely randomized design. Survey study revealed that sowings of wheat after first fortnight of November have significantly higher number of farm fields with medium control (control 50 to 60%) (3.0 farm fields) to low control (control less than 50%) (6.3 farm fields) environments of P. minor. High control environment (control more than 60%) has significantly higher number of farm fields (11.7) with less infestation of P. minor (population of P. minor less than 5 plants per square meter). However, in low control environments higher number of farm fields has population of P. minor 15 and more than 15 plants per square meter. P. minor appeared more in significantly higher number of farm fields (14.3), (3.7) and (7.7) in high control, medium control and less environment, respectively in the month of December. Significantly higher number of farm fields (16) used recommended herbicide to control P. minor in wheat crop in high control environment. However, farmers apply unrecommended herbicide in higher number of farm fields. Herbicide was applied timely to control P. minor in wheat crop in significantly higher number of farm fields (14) in high control environment. In low control environment farmers applied herbicide late to control P. minor in significantly higher number of farm fields (8.0). Farmers used right type of nozzle (Flat Fan and Flood Jet) to apply herbicide to control P. minor in significantly higher number (14) of farm fields in high control environment. Farmers used wrong type of nozzle to apply herbicide to control P. minor in more number of farm fields in medium control and less control environments. Optimum volume of water (150 litres of water per acre) was used to apply herbicide to control P. minor in wheat crop in significantly higher number of farm fields (17) in high control environment. Farmers used low volume of water (100 to 125 litres per acre) to apply herbicide to control P. minor in significantly higher number of farm fields (8.0) in low control environment. Farmers did not practice herbicide rotation in significantly higher number of farm fields 4.0 and 8.0 in medium control and low control respectively. P. minor inflorescence was not removed by farmers in significantly higher number of farm fields 4.0 and 8.0 in medium control and low control environments respectively. Inaproppropriate herbicide selection, method of application, delay in sowing of wheat and application of herbicide, lack of herbicide rotaion and non-removal of P.minor inflorescence were the reasons for poor control of P. minor in wheat crop.

Conventional weed control methods often have environmental impact. The present study was conducted to screen selected accessions of Pseudomonas for both potential biocontrol of Phalaris minor and Avena fatua and potential concurrent growth promotion of wheat. The four Pseudomonas strains (B11, T19, T24, and T75) were found positive for cyanide production, siderophore production, phosphorus solubilization, oxidase activity, catalase activity, and ACC deaminase activity in vitro. These strains were phytotoxic, causing up to 73.3% mortality in the lettuce seedling bioassay. Consortia of compatible Pseudomonas strains increased A. fatua and P. minor seedling mortality up to 50.0% and 56.7%, respectively, and reduced root length up to 73.8% and 53.9%, respectively, as compared with the uninoculated control. Consortia of compatible Pseudomonas strains increased wheat shoot length, root length, fresh biomass, dry biomass, and leaf greenness up to 41.6%, 100%, 79.9%, 81.5%, and 21.1%, respectively, over the uninoculated control. Four of the 11 Pseudomonas consortia tested expressed good weed suppression and wheat growth promotion capacity and deserve further experimentation. The findings from this study may lead to the formulation of bioherbicides that will improve human and environmental health.

The herbicidal potential of nine phenolic acids including p-hydroxybenzoic acid, protocatechuic, syringic, vanillic, gallic, salicylic, ferulic, p-coumaric and caffeic acid were evaluated against Corchorus olitorius and Phalaris minor weeds at the concentrations of 5, 10 and 20 mM. The effectiveness of phenolic acids on germination depended on target seed, specific phenolic acid and concentration. The inhibitory effects varied between the two tested seeds, and P. minor was the more sensitive. With few exceptions, phenolic acids at all tested doses did not inhibit seed germination of C. olitorius, but the acids caused great inhibition effects on germination of P. minor. Salicylic acid nearly had a complete inhibition effect on germination of tested seeds when used at 20 mM. P-hydroxybenzoic, protocatechuic, salicylic, vanillic and ferulic acids appeared great inhibition effects on germination of P. minor and nearly had complete inhibition effects when used at high dose. In a greenhouse trial, we found that application of phenolic acids at 5–20 mM did not produce any significant effect on growth on 5‑weeks-old C. olitorius or P. minor plants, after seven days from treatments. The study concluded that phenolic acids had diverse activities on germination and growth of C. olitorius or P. minor weeds.

Wheat [Triticum aestivum L. (Poaceae)] is the staple diet of people in Pakistan. It is attacked by many types of pests. Therefore the purpose of this study was to assess the impact of climate change on the ecology and epidemiology of various wheat pests in Punjab, Pakistan. Results indicate that maximum weeds hot spots 242 (5.98%) Phalaris minor, 45 (1.18%) wild oat and 203 (5.01%) broad leaf weeds were noted in 2015. Aphid 31 (0.86%) hot spots were recorded in 2016 while maximum army worm 13 (0.26%) hot spots were noted in 2017. Maximum 70 (1.73%) spots of yellow rust and 85 (2.10%) hot spots of brown rust were observed during 2015 while 84 (4.16%) spots of loose smut were observed during 2017. ANOVA shows that years have no significant difference (P > 0.05) but weeks have significant effect on occurrence of these pest incidences except brown rust. But regression ANOVA was significant (P ≤ 0.05) and regression models equations have been developed on the bases of recorded data. Pest incidence was taken as dependent variable Y and weather factors i.e. minimum temperature as X1, maximum temperature as X2, relative humidity as X3 and rain fall as X4 were taken as independent variables. This study will help in recommendations for moving forward aiming at integration of biology of rust and smut diseases of wheat with changing climate for development of resistant varieties for resilient and durable management of these pathogens.

Rice (Oryza sativa L.)-wheat (Triticum aestivum L.) is the predominant cropping system of North Indian region. Due to continuous following of rice-wheat cropping system every year, weed infestation particularly in wheat, has emerged a major problem resulting in reduced wheat yield and nutrient mining. Integration of suitable planting methods, along with effective weed control measures, can reduce the weed infestation and nutrient mining from the soil and can enhance available plant nutrients in the soil. To evaluate the influence of different planting techniques and weed control practices in wheat on available plant nutrients in soil, a field study was conducted at the department of Agronomy, Punjab Agricultural University, Ludhiana (India) for two consecutive years. The treatments comprised of five planting techniques: conventional tillage, zero till sowing without rice stubbles, zero till sowing in standing rice stubbles , zero till sowing after partial burning of rice stubbles and bed planting and five weed control treatments i.e. clodinafop 60 g/ha, clodinafop 60 g/ha fb 2, 4-D 0.5 kg/ha, sulfosulfuron 25 g/ha, mesosulfuron + iodosulfuron 12 g/ha and unweeded (control). The experiment was conducted in split plot design with planting methods in the main plot and herbicidal treatments in the sub plot with three replications. The results of the study showed that zero till sowing of wheat in standing rice stubbles observed significantly higher soil organic carbon, available nitrogen, phosphorus and potassium than conventional till wheat sowing after removal of rice residues. Although partial burning of rice stubbles also showed positive trend in soil organic carbon, available nitrogen, phosphorus and potassium but retort was less distinct than rice stubbles without burning. Further, zero tillage alone also showed improvement in soil organic carbon and available nitrogen, phosphorus and potassium over conventional tillage. Application of herbicides did not diverge soil organic carbon, but significantly improved the available nitrogen, phosphorus and potassium content in soil than the unweeded (control).

The genus Phalaris (Poaceae) is comprised 21 species, which is distributed in temperate areas of both northern and southern hemispheres and the mountains of tropical Africa and South America. Phalaris minor and Phalaris paradoxa are highly competitive weeds in winter cropping systems involving cereals, pulses, pastures, horticultural, ornamental crops, and vineyards. Both species produce a large number of seeds with varying forms of dormancy, although their half-life in the soil seed bank is relatively short. The yield losses in wheat due to P. minor and P. paradoxa may be up to 50% and 40%, respectively. Both species are prolific seed producers, short-lived, and exhibit periodicity of emergence. With the increase in concerns about the environment and human health issues, there is a greater emphasis on predicting the emergence pattern of weed species in relation to soil environmental conditions. The cornerstone for effective weed management relies on various aspects related to seed germination, dormancy, viability, loss of vigor, and resultant seed bank dynamics and its distribution pattern in the soil. In this chapter, we described biology and ecology along with molecular, physiological, and agronomic aspects involved in herbicide resistance observed in biotypes of these weed species. New selective herbicides are needed to augment those currently available to overcome present and future resistance problems. Integrated weed management strategies involving herbicide rotation and/or mixture with different modes of action and other cultural control measures will help to reduce selection pressure and prevent further spread and evolution of herbicide resistance in Phalaris species across different continents.

Application of allelopathic bacteria (AB) for weed suppression may be helpful to solve various environmental challenges posed by conventional weed control techniques. In our earlier studies, around 400 strains of rhizobacteria of five weeds and wheat were isolated, screened for production of phytotoxic substances, and tested for phytotoxic activity on wild oat and little seed canary grass, and possible effects on wheat under laboratory conditions. We obtained 13 strains inhibitory to wild oat (Avena fatua L.) and 11 to little seed canary grass (Phalaris minor Retz.). Five of these (13 and 11) strains also suppressed wheat (Triticum aestivum L.) while others either stimulated or remained ineffective on wheat in separate bioassays. The success of any weed biocontrol technique, however, depends on its response under field conditions. Therefore, the present study was conducted to investigate biological weed control of the five most efficient strains of AB under natural conditions in pot and field trials. Wheat was artificially invaded with wild oat in the pot trial through seeding. Wheat of the field trial was artificially invaded with wild oat and little seed canary through seeding. The selected strains belonged to pseudomonads (Pseudomonas putida, P. fluorescence, P. aeruginosa, and P. alcaligenes) and their inocula were prepared using sterilized peat. The inoculated seeds of wild oat and wheat were sown together in a pot trial. The inoculated seeds of wild oat, little seed canary grass, and wheat were sown together in the field experiment. The field was selected based on chronic infestation of these weeds. However, weed invasion was ensured by adding seeds of weeds (inoculated with the respective strains of AB, according to treatment plan). A severe invasion of wild oat was observed in the pot trial, which reduced the grain yield of infested wheat up to 60.8%. The effectiveness of applied strains controlled 22.0&ndash, 76.3% loss of grain yield of infested wheat. Weed invasion in the field trial reduced the grain yield of the crop up to 56.3% and effectiveness of the applied strains controlled 29.0&ndash, 60.7% loss of grain yield of infested wheat. The study of other agronomic, physiological, and chemical parameters of the crop and weeds supported these findings. Harnessing the potential of these strains exhibited in our studies may be helpful to introduce an innovative, sustainable, and eco-friendly weed control technique for production of wheat.

Wheat is the staple cereal crop of Pakistan but its growth is rigorously affected by associated weeds. Present study evaluated the synergistic effect of plant antagonistic rhizobacteria and fungi on growth, yield and suppression of wheat-associated weeds. Wheat associated weeds Phalaris minor and Avena fatua were grown in pots containing wheat as well. Pseudomonas aeruginosa strain PAO1 and Trichoderma harzianum T-MN6 were used as amendments to check their effect on two major weeds of wheat. The combined application of PAO1 and T-MN6 reduced the shoot length of Phalaris minor up to 30% and Avena fatua 40%, root length 22% and 28%, fresh biomass 29% and 31% respectively over their sole application. Similarly, inoculation of PAO1 and T-MN6 alone and in combination considerably enhanced growth, yield and physiological parameters of wheat. It was inferred from this study that the synergistic application of PGPR and fungi is a promising option to suppress major weeds of wheat and to enhance growth and yield of wheat.

Climatic conditions for seed germination of four weed species, Avena fatua, Bromus catharticus, Chenopodium album and Phalaris minor, which occur commonly in cereal fields in the north of Saudi Arabia, were compared. Proportionately, most seeds of the two collected seed lots germinated during the first three weeks of the experiment, confirming an early response pattern. Overall, germination was higher in Bromus catharticus, Avena fatua and Phalaris minor than Chenopodium album. Compared to the other species, proportionately more Phalaris minor seeds germinated in the second period, indicating a higher propensity for slow germination. Germination in all species favoured alternating temperatures (10/20 °C or 5/25 °C) over a constant (15 °C), in a light/dark (16/8 h) regime. However, Avena fatua and Bromus catharticus seeds also showed significant germination in a dark only (24 h) regime, indicating light has less influence on their germination. Variation in germination between geographically separate seed collections of all four species was significant in some conditions, however, the general pattern was of similar responses between the two seed lots. Results determined that, in respect of interactions between temperature and light, the most important climatic condition for maximum seed germination, in all four weed species, is alternating temperatures. The outcomes of this study can lead to the expected timings of weed species' germination and dispersal in field conditions, and are used to make recommendations for practical weed control measures. Keywords: Avena fatua, Bromus catharticus, Chenopodium album, Phalaris minor, Climatic conditions, Weeds, Seed germination, Saudi Arabia

The effect of the aqueous extracts and crude powder of the aerial shoots of Retama raetam (donor species, Fabaceae) on germination and some growth and physiological parameters as well as protein profile and antioxidants of both Triticum aestivum and Phalaris minor (recipient species, Poaceae) was evaluated. The experiments were applied in pure and mixed cultures through germination and growth bioassays. The phytochemical screening of Retama raetam indicated the presence of some water-soluble phytotoxins (allelochemicals) allowing this plant to be an alternative management (bioherbicid) of Phalaris minor in wheat fields. Data revealed that germination percentages (GP) of T. aestivum and P. minor grains significantly (p ≤ 0.05) decreased with increasing the concentration of the aqueous extract. Notably, GP decrement varied according to the species as well as the treatment, but in all cases 40% concentration level was shown to be the most effective concentration. Seedling length (SL), fresh (FW) and dry (DW) weights of T. aestivum and P. minor grains in pure and mixed cultures experiments 21 days after sowing were also affected by R. raetam crude powder. Furthermore, protein expression of both T. aestivum and P. minor as affected with R. raetam crude powder was noticeable and new proteins have been expressed in the treated plants as compared to control. The use of allelopathic potential of the invasive species under the present study has been suggested as a viable option in sustainability as bioherbicide.

Phalaris minor Retz., P. paradoxa L. and P. brachystachys Link. are prolific and competitive and considered as winter crops weeds. All three Phalaris species. The objective of the study was to obtain information about germination responses of P. minor, P. paradoxa and P. brachystachys to constant temperatures, drought and salt stresses, pH and seedling emergence to planting depth in laboratory and pot experiments. Interaction effect of constant temperatures and light regimes significantly influenced on seed germination of all three Phalaris species. With an increase in temperature from 10 °C to 30 °C, germination of all three Phalaris species was reduced. At 30 °C, 9.6% of P. minor seeds geminated, but no seed germination of P. paradoxa and P. brachystachys was observed. Both drought and salt stresses decreased germination of Phalaris species. Phalaris minor was able to germinate at higher levels of drought and salt stresses in comparison to P. paradoxa and P. brachystachys. Seeds of P. minor and P. paradoxa were germinated at pH ranges from 4 to 8, and all three Phalaris species germination was inhibited by pH higher than 8. Seedling emergence markedly affected by planting depth and Phalaris species interaction and reduced as planting depth increased. These results showed that germination of all three Phalaris species was affected by environmental conditions. Phalaris minor germinated over a wider range of environmental conditions than P. paradoxa and P. brachystachys, which explain why P. minor is more widespread within cropping systems.

A field survey was conducted for the sampling of Acetyl-CoA carboxylase (ACCase) inhibitor resistance littleseed canarygrass, a major weed of wheat, from Punjab, Pakistan in 2014 for confirmation of resistance. The surveyed regions encompassed four different cropping systems including rice–wheat, maize–wheat, cotton–wheat and mixed cropping. Dose–response assay was conducted for confirmation of resistance. Efficacy of herbicide mixtures including clodinafop–propargyl, metribuzin, pinoxaden and sulfosulfuron at a range of doses was investigated to manage littleseed canarygrass. Results revealed that all populations were resistant to fenoxaprop except PM-BWL-2. The higher level resistance (6.5) was found in populations collected from rice–wheat cropping system. The tested herbicide mixtures at 75% and 100% of the recommended dose of each mixture component provided the effective control of resistant littleseed canarygrass. Mixtures at 50% provided more than 80% control and reduced growth and seed production potential of surviving plants. The confirmation of ACCase inhibitor resistance as the first case of herbicide resistance in Pakistan, leads us to discourage use of ACCase inhibitor herbicides alone. However, herbicide mixtures at 75% and 100% of the recommended dose are suggested to manage this weed for sustainable wheat production in the surveyed cropping systems.

Use of herbicide mixtures has been advocated as most effective strategy for avoidance and management of herbicide resistant weeds. Effect of twelve selected treatments of four herbicides (clodinafop-propargil, metribuzin, pinoxaden and sulfosulfuron) two-way mixtures at different doses was investigated against fenoxaprop-p-ethyl resistant and susceptible populations of P. minor grown along the wheat plants. In repeated experiment, herbicides mixtures were applied at 3 to 4 leaf stage of P. minor under greenhouse conditions. All the herbicide mixtures were effective to control resistant as well as susceptible P. minor. Mixtures having 75% lethal dose of each mixture component provided best control against P. minor. Mixtures with 50% lethal dose of each herbicide also provided more than 80% control of P. minor. Surviving P. minor plants after exposure to herbicide mixtures showed reduced growth and seed production potential. No mixture combination produced phytotoxic effects on wheat plant up to 75% of lethal dose of each mixture component. Mixtures including clodinafop-propargil + metribuzin, pinoxaden + sulfosulfuron and pinoxaden + metribuzin at 100% dose of each mixture component produced minor phytotoxic effects on wheat plants and caused no reduction in terms of ultimate growth and grain yield. However, mixture of sulfosulfuron + clodinafop-propargil at 100% dose of each component was phytotoxic to wheat and caused significant reduction in term of growth and grain yield. So, farmers can use these mixtures even at 75% of recommended dose of mixture component to control susceptible and resistant P. minor in wheat. RESUMO O uso de misturas de herbicidas tem sido visto como a estratégia mais eficaz para prevenção e controle de plantas daninhas resistentes a herbicidas. Os efeitos de 12 tratamentos, selecionados entre quatro herbicidas (clodinafop-propargil, metribuzin, pinoxadene e sulfosulfuron) com misturas de duas vias em doses diferentes, foram estudados para as populações de P. minor resistentes e suscetíveis ao fenoxaprop-p-ethyl e que cresciam ao longo de plantas de trigo. Em experimentos repetidos, as misturas de herbicidas foram aplicadas em três a quatro estádios de crescimento da folha de P. minor em casa de vegetação. Todas as misturas de herbicidas foram eficazes para controlar plantas de P. minor resistentes e suscetíveis. As misturas com 75% de dose letal de cada componente ofereceram melhor controle de P. minor. As misturas com 50% da dose letal de cada herbicida também proporcionaram controle de mais de 80% de P. minor. As plantas que sobreviveram após serem expostas às misturas de herbicidas apresentaram deficiência de crescimento e de produção de sementes. Nenhuma combinação das misturas gerou efeitos fitotóxicos para o trigo em até 75% da dose letal de cada componente. As misturas com clodinafop-propargil + metribuzin, pinoxadene + sulfosulfuron e pinoxadene + metribuzin a 100% da dose de cada componente produziram leves efeitos fitotóxicos em plantas de trigo e não causaram redução em termos de crescimento final e rendimento de grãos. No entanto, a mistura de sulfosulfuron + clodinafop-propargil a 100% da dose de cada componente foi fitotóxica ao trigo e causou redução significativa do crescimento e produtividade de grãos. Portanto, os agricultores podem utilizar essas misturas, mesmo a 75% da dose recomendada de componente, para controlar plantas de P. minor suscetíveis e resistentes ao trigo.

THE PRESENT study was concerned with the synthesis of AgNPs via application of Haplophyllum tuberculatum crude aqueous extract (HTCAE) as a reducing agent. The resultant extract (HTAgAE) together with the crude one was compared in testing growth and some physiological and molecular parameters of the two recipient species; Triticum aestivum L. as a crop species and Phalaris minor Retz. as weed species. The effect of HTCAE on P. minor revealed significant reduction in growth germination percentage and both radicle and plumule lengths, nevertheless HTAgAE completely inhibited its germination. The HTAgAE at 5% and 10% stimulated the photosynthetic pigments in T. aestivum and reduced them in P. minor at 20% of HTCAE and HTAgAE. The total number of bands, polymorphism percentage and genomic template stability (GTS) % were generally arranged in a descending order by using HTCAE and HTAgAE. This order was reversed with HTAgAE in P. minor at 5% and in T. aestivum at 5% and 20% that reflected antagonistic effect of the nanosilver extract. At 5% HTCAE and 20% HTAgAE, T. aestivum accomplished more genetic stability than P. minor which may support their use as safe bioherbicide.

Evolution of herbicide resistance in weeds is among the serious challenges that agriculture face today. In Pakistan herbicide use over last 6 decades has enabled earlier planting of short-season crops and improved weed control in wheat as well as other cropping systems. This has greatly favored the use of more and more herbicides. Conversely, this exercise increased the evolution of resistant biotypes. Wheat being Pakistan's number one staple crop faces daunting weeds problem. In order to understand the status of herbicide resistant weeds in wheat fields, survey was conducted for two consecutive years (2015-2017) in different regions of Pakistan. A questionnaire was designed to collect data from three hundred farmers randomly selected in all four provinces of Pakistan on herbicides used in wheat, history of crop cultivation regimes and weed species that have seized to respond to field rates of herbicides. Seed of suspected biotypes were collected from the survey sites and preserved in our gene pool for the confirmation of the resistance in the laboratory by bioassay and molecular level in future. Farmers (96%) perceived that Phalaris minor Retz. was the most important annual weed of wheat crop followed by Avena fatua L. (94%). Customarily, three aryloxyphenoxy propionate herbicides, clodinafop-propargyl, fenoxaprop-P-ethyl and diclofop-methyl were used to control different grass weeds such as P. minor, A. sativa L. and A. fatua. In farmers' opinion, high yield of wheat was associated with the continuous use of these herbicides. Resistance-suspicious weeds were reported from all studied areas (Punjab, KPK, Sindh, and Baluchistan provinces) in fields with the herbicide use history of five to seven years or more. This study suggests that for long-term avoidance of herbicide resistance, in our wheat growing systems we will require embracing practices that decrease selection pressures favoring resistant weeds. Achieving these goals requires an understanding of the evolution and dynamics of resistant populations. It is recommended that for the effective management of resistant populations of P. minor and A. fatua, farmers' education on ecologically sustainable weed management is critically important. This study will provide a basis for examining the questions that are relevant to understanding herbicide resistance evolution in Pakistan and that may help determine appropriate weed management strategies.

Residue incorporation greatly modifies the soil chemical properties, and regulates seed germination and subsequent growth of neighboring species by inducing metabolic changes. Such growth regulatory effects often vary among cultivars and the stage of growth of donor plants. Little information is available on the induced biochemical changes in receiver plants and the soil chemical properties when wheat residue collected at different growth stages is incorporated into the soil. Bioassays were conducted to appraise the allelopathic potential of residue (8 g kg soil) of hexaploid wheat (Triticum aestivum L.) cultivars (Millat-2011, AARI-2011, Lasani-2008 and Faisalabad-2008) collected at tillering (Z-30), anthesis (Z-60) and maturity (Z90)] against canary grass (Phalaris minor Retz.). Mean emergence time of canary grass was prolonged over control by soil incorporation of residue at anthesis and maturity stages of cultivars AARI-2011 and Lasani-2008. Final emergence percentage declined by 13‒31% for residue collected at different growth stages. Maximum suppression in shoot (33‒51% and 28‒53%) and root (34‒52% and 28‒54%) length and seedling dry biomass (66‒88% and 58‒86%) of canary grass over control was also recorded under aforementioned treatment combinations. Total chlorophyll contents in canary grass declined in response to soil incorporation of residue at anthesis and maturity stages of all wheat cultivars but an increase was recorded for residue incorporated at tillering stage. Phenolic contents in residue and residue-amended soil increased with advancement in stage of wheat growth. Biochemical bases of phytotoxicity and changes in activities of enzymatic antioxidants in canary grass seedling are discussed. Such information suggests the growth regulatory potential of residue of specific wheat cultivars against weeds of economic significance in wheat based cropping systems and scope for increasing nutrient status of soils. © 2016 Friends Science Publishers

Littleseed canarygrass is a major weed of wheat in rice–wheat cropping system of North-West India. The present study was conducted to study the role of ethylene in germination ecology and seedling growth of littleseed canarygrass and wheat using cobalt chloride (inhibitor of ethylene synthesis) and ethephon (ethylene source). Cobalt chloride at concentrations ≥0.1 mM caused significant reduction in germination (%), germination index and increased the mean germination time of littleseed canarygrass, whereas wheat seeds exhibited significant decrease in germination (%) at cobalt chloride concentrations ≥0.5 mM. Cobalt chloride at higher concentrations significantly reduced the seedling growth of littleseed canarygrass and wheat with more pronounced effect on root length as compared to shoot length. It also significantly increased the membrane leakage and soluble sugar content of seedlings of both species with concomitant decrease in chlorophyll and protein content. Ethephon at 0.1 and 1 mM concentrations significantly increased the germination (%), speed of germination with concomitant decrease in mean germination time as compared to control. Ethephon concentrations 0.1 and 1 mM had no effect on membrane leakage, total soluble sugars and protein content but increased the chlorophyll content in seedlings of both species. Seed dormancy of littleseed canarygrass induced by higher concentrations of cobalt chloride, i.e., 2.5 and 5 mM could also be overcome by treatment with 1 mM ethephon, confirming the role of ethylene in germination of this weed.

Littleseed canarygrass (Phalaris minor Retz.) is a most dominant weed of wheat (Triticum aestivum L.) in the north-western states of India. Little information is available on germination of littleseed canarygrass and wheat under similar ecological conditions. The present study was conducted under controlled conditions to study germination ecology of littleseed canarygrass population possessing multiple-herbicide resistance, along with wheat. Germination of littleseed canarygrass and wheat was independent of light. Optimum temperature for germination of littleseed canarygrass and wheat was 20°C. Germination of both species was completely inhibited at osmotic potentials lower than −0.4 MPa. Seeds of littleseed canarygrass and wheat were able to germinate even at NaCl concentration of 200 mM, with complete inhibition at 300 mM. Germination of both species was favored in a pH range of 5–8. Moisture, salinity, and pH stresses significantly reduced the speed of germination, with a concomitant increase i...

Because cropping systems can greatly affect the establishment and spread of alien species populations, the design of cropping systems to control invasive weeds is an important approach for invasive species management in agro-ecosystems to avoid excessive increases in other control measures such as herbicides. The annual weed Phalaris minor Retz. (P. minor) is one of the most troublesome invasive weed species of winter crops in Yunnan Province, China, but the development of cropping systems for ecological control of this weed have received limited research attention. Here, we studied seed dormancy, germination characteristics and reproductive responses of P. minor to various cropping systems to show how cropping systems could be better designed to control P. minor in China. Our research showed that cropping systems significantly affected seed dormancy in submerged paddy fields. Phalaris minor seed remained dormant and the germination rates (less than 10%) were significantly lower (p &lt, 0.05) than in maize fields and dry, bare soil conditions. Wheat, faba bean and rapeseed crops had no significant influence (p &lt, 0.05) on the seed germination rate of P. minor, but increasing soil depth significantly decreased (p &lt, 0.05) the germination rate and germination index of this weed. Total biomass, spike biomass, spike number and seed number of P. minor were significantly reduced (p &lt, 0.05) with increasing proportions of the three crops (wheat, faba bean and rapeseed), with rapeseed having the strongest inhibition effects among the three crops. The reproductive allocation and reproductive investment of P. minor were also significantly reduced (p &lt, 0.05) in mixed culture with wheat and rapeseed. With increasing proportions of wheat or rapeseed, the specific leaf area of P. minor significantly increased (p &lt, 0.05), but the reverse was true for leaf area and specific leaf weight. Moreover, the net photosynthetic rate, stomatal conductance and transpiration rate for P. minor also decreased significantly (p &lt, 0.05) when grown with wheat or rapeseed. These results suggest that optimal cropping systems design could involve planting rapeseed in conjunction with deep plowing and planting rice (continuous submergence underwater) in summer. Such a system could reduce the field populations and seed bank of P. minor, thus providing a sustainable and environmentally friendly means of suppressing P. minor.

Herbicide resistance is an evolutionary process that may involve changes in physiological and ecological traits related to plant fitness. This type of resistance occurs in littleseed canarygrass ( Phalaris minor ). This study was aimed to determine the effect of resistance to ACCase-inhibiting herbicides on fitness of seed accessions of littleseed canarygrass. Seed characteristics are important because they may determine the outcome of competition between susceptible (S) and resistant (R) biotypes. Experiments were performed to determine whether differences between S and R accessions in embryo size, dormancy, longevity, and germination speed might occur. Differences in plant fitness associated to herbicide resistance were found in seed physiological characteristics. The embryo size of R accessions was reduced up to 50 % (on a dry weight basis), which resulted in an increase in the number of days required to germinate and a reduction in the germination speed. Damage to membranes, which is related to longevity, was more severe in the R accessions. The observed decrease in seed vigor could affect the establishment of seedlings, which may explain the low success of R accessions under herbicide selection pressure.

Isoproturon is a pre- and post-emergence herbicide used generally to manage Phalaris minor and Avena ludoviciana in wheat. The importance of post-emergence and foliarly applied pesticides has been increasing. The first reaction environment of these herbicides is the leaf surface made up of polymerised esters of higher fatty acids. In the presence of sunlight, the fatty substances on leaf surfaces generate reactive radicals, or ions which may interact with herbicide molecules leading towards degradation resulting in the loss of bioefficacy of herbicides and the formation of metabolites of unknown toxicity. The present experiment was conducted with the objective to know the photochemical behaviour of isoproturon on different leaf-extracted epicuticular cutin surfaces. Epicuticular waxes, i.e. cutins were extracted from P. minor and A. ludoviciana leaf surfaces using dichloromethane as a solvent and further purified with activated charcoal. On the cutin surface under UV-light (365 nm), the transformation of the herbicide is very slow as it is evident from its higher half-life values, 75 min on P. minor cutin surface and 115 min on A. ludoviciana cutin, as compared to that on the glass surface (half-life 53 min). A similar pattern was also observed under the sunlight condition. It may be due to the quenching effect imparted by the cutin material or simply screening effect of it on the herbicide. The sunlight-irradiated extracts of isoproturon and its degradation products were analysed by LC–MS/MS using electrospray interfacing technique and the structures of six different photoproducts were characterised by their respective spectra. The degradation pathways involved mainly demethylation and ring oxidation processes forming hydroxylated compounds. The mixture of these photoproducts were found to be non-toxic to A. ludoviciana and P. minor.

The aim of the present study was to determine the nutritional value of Phalaris minor seeds in comparison to conventional cereal grains. P. minor seeds had higher ether extract (6.3%), total ash (7.5%), acid insoluble ash (AIA, 4.5%), acid detergent fibre (ADF, 10.2%), cellulose (5.5%), acid detergent lignin (ADL, 2.0%), neutral detergent insoluble crude protein (NDICP, 4.0%) and acid detergent insoluble crude protein (ADICP, 2.7%) content in comparison to conventional cereal grains. The crude protein of P. minor seeds (12.3%) was similar to that of wheat (12.0%), but higher than other conventional cereal grains including maize (9.0%). The amino acid composition of P. minor seeds was more or less similar to conventional cereal grains. P. minor seeds had a superior mineral profile (Ca, P, Na, K, Mg, Fe, Cu, Zn and Mn) than conventional cereal grains. In vitro evaluation revealed that net gas production was lowest (P less than 0.05) in P. minor seeds (216.37 L/kg DM/24 h). The methane production (L/kg DM/24 h)from P. minor seeds (43.03)was lower (P less than 0.05) than that from wheat (54.33) and barley (57.35). The organic matter digestibility of P. minor seeds (83.27%) was similar to that of barley (81.69%).It was concluded that P. minor seeds could be considered as potential source of nutrients for livestock.

Pot culture experiments were conducted to find out the effect of different cropping conditions, depth of burial and age of seeds on the survival of little seed canary grass (Phalaris minorRetz.) seeds. The results indicated that the soil temperature modifications through the flooding or filed capacity moisture status of the soil influenced the germination and viability of the buried weed seeds rather than the cropsper se. It was observed that the seeds lost their viability because of the anaerobic conditions and high temperatures and through increased membrane permeability of the seeds. TheP. minorRetz. seeds were found to be sensitive to anaerobic conditions. The longevity of seeds buried in rice-wheat system and Flooding-wheat system was found low when compared to those buried under soybean-wheat and field capacity-wheat conditions. Thein situeffect of rainy season (kharif) crops was found to confine to influencing the initial germination (vigor) of the little seed canary grass with cowpea, groundnut, soybean and sunflower inhibiting the initial germination of little seed canary grass. This inhibition was absent at the end of germination counts taken after twenty days after keeping for germination. The residual effect of cowpea, rice, soybean and sunflower was observed. The application of pearl millet and rice residues has considerably reduced the little seed canary grass germination, plant height, seedling fresh weight and leaf area at thirty days after sowing.

Bipolaris sorokiniana, causal agent of spot blotch of wheat is a hemibiotrophic pathogen. This fungus produced a toxin in culture that induced necrosis not only in wheat but also in barley, sorghum and some weeds. The toxic compound purified by prep TLC from culture filtrate of virulent strain BS-75, characterized using NMR and GC-MS techniques, was identified to be ‘Bipolaroxin’, which is a first report of its production by B. sorokiniana infecting wheat. It is a bicyclical sesquiterpene belonging to family Eremophilane. Besides producing necrotic lesions on wheat, toxin (30 ng/ml) caused necrotic lesions on barley, maize, sorghum, Phalaris minor, Avena sativa and Cynodon dactylon as studied using leaf infiltration bioassay. Qualitative and quantitative differences among the pathogenically variable isolates were observed with respect to toxin production by TLC and HPLC. Different isolates produced bipolaroxin in the range of 0.05 µg/ml (BS-41) to 1.4 µg/ml (BS-75).

Hormesis is a biphasic dose response to an environmental agent characterized by low dose stimulation and high dose inhibitory or toxic effect. In order to develop an effective weed management system, the stimulatory and/or inhibitory response of low doses of herbicides on germination and growth of weeds should be considered. Thus, a laboratory study was conducted to test the effect of low dosages of 2,4-D on wheat (Triticum aestivum L.) and associated dicotyledonous weeds. Low dosages of 2,4-D (0, 5, 10, 20, 40 and 50 g/ha) failed to accelerate either seed germination or seedling growth of T. aestivum and tested four weed species -Phalaris minor Retz., Avena ludoviciana Durieu., Medicago denticulata Willd. and Rumex dentatus L. under in vitro conditions in Petri-dishes. The application of 2,4-D inhibited the seed germination and seedling growth of these weeds in a dose dependent manner with higher concentrations being more inhibitory. The sodium formulation of 2,4-D more adversely affected the germination of P. minor and A. ludoviciana as compared to its ethyl ester formulation. The results indicated that 2,4-D when used as a post-emergence herbicide in wheat fields can delay the emergence of new flushes of weeds like P. minor, A. ludoviciana, M. denticulata and R. dentatus due to its inhibitory effect on their germination. It could be concluded that low doses of 2,4-D did not enhance germination/seedling growth of wheat and associated weeds.

A replacement series study was conducted to evaluate the interference interactions between the weeds Phalaris minor or Rumex dentatus and wheat at two nutrient levels to test for changes in the competitive relationships of the weeds with varying nutrient availability. Plants were established in a mixture with proportions of 4:0, 3:1, 2:2, 1:3 and 0:4 (wheat: weed) plants per pot. The weeds exhibited clear differences in growth attributes and competition indices from wheat. Rumex dentatus showed significantly higher values for all growth attributes, relative yield, aggressivity and biomass. Both weeds performed better than wheat at high nutrient levels. Nutrient stress changed the intensity of competition between weeds and wheat, but did not change the weeds’ positions in the hierarchy. Therefore, although the competitiveness of P. minor and R. dentatus appears to be lower under poor nutrient conditions, they outcompete wheat irrespective of nutrient availability. Overall, the findings of the study suggest...

This work was aimed to evaluate the essential oil from root of medicinally important plant Senecio amplexicaulis for chemical composition, antifungal and phytotoxic activity. The chemical composition analysed by GC/GC–MS showed the presence of monoterpene hydrocarbons in high percentage with marker compounds as α-phellandrene (48.57%), o-cymene (16.80%) and β-ocimene (7.61%). The essential oil exhibited significant antifungal activity against five phytopathogenic fungi, Sclerotium rolfsii, Macrophomina phaseolina, Rhizoctonia solani, Pythium debaryanum and Fusarium oxysporum. The oil demonstrated remarkable phytotoxic activity in tested concentration and significant reduction in seed germination percentage of Phalaris minor and Triticum aestivum at higher concentrations. The roots essential oil showed high yield for one of its marker compound (α-phellandrene) which makes it important natural source of this compound.

Gherekhloo J, Osuna MD & De Prado R (2012). Biochemical and molecular basis of resistance to ACCase-inhibiting herbicides in Iranian Phalaris minor populations. Weed Research52, 367–372. Summary Phalaris minor is a common weed in wheat and barley fields of Iran. Repeated use of ACCase inhibiting herbicides during the last two decades to control this weed has resulted in the appearance of populations of P. minor that are resistant to the aryloxyphenoxy propionates (APP) in some wheat fields of the country. Dose–response assays were conducted to investigate the level of resistance in two P. minor populations (AR and MR4) which have developed resistance to three APP herbicides, including diclofop-methyl, fenoxaprop-P ethyl and clodinafop propargyl. A high level of resistance in these populations may be due to the presence of an altered ACCase enzyme in these plants, and we hypothesised that one or more mutations in the gene encoding ACCase enzyme are responsible for insensitivity of the enzyme. Results confirmed that resistance in both populations was target site-based, and molecular studies revealed that substitutions of Trp-2027-Cys and Asp-2078-Gly, respectively in AR and MR4, are responsible for insensitivity of the enzyme in these populations. This is the first report to show that these substitutions endow resistance to APP herbicides in P. minor, though other resistant biotypes are reported from elsewhere. These mutations may result in resistance of P. minor to some DIM and DEN herbicides. It seems that lack of adequate herbicide and crop rotation has selected plants with different target site mutations, which cause differential responses of the ACCase enzyme to ACCase inhibitors. Additional resistance management practices may be necessary to prevent ACCase-inhibiting herbicides from becoming ineffective over wide areas.

Two field experiments were performed at 2009/2010 and 2010/2011 to study the interaction effect between biofertilizers and fusilade herbicide at (1.5 L/fed. as a recommended dose) alone and in combination with additives at (1.0 L/fed.) to enhance narrow weeds control and broad bean productivity. During the two seasons, a positive correlation was found between biofertilizers and broad bean plant height, number of branches, number of nodules, fresh and dry weight, seed germination as well as number and activity of soil microbes. Inoculated broad bean seeds with Rhizobium leguminosarum ordual inoculation with (Rhizobium leguminosarum plus Bacillus megaterium) were encourage the capability of the plants to produce vigorous vegetable growth and increasing yield productivity of broad bean than non bio-fertilized treatment. The inoculation with R. leguminosarum as a single inoculants or dual inoculants with B. megaterium increased microorganism densities and activity which reflected on broad bean growth, yield and tolerability to the stress of fusilade herbicide. During1styear fusilade at micro rate (1.0 L/fed.) with mineral oil achieved the maximum inhibition in Phalaris minor fresh and dry weigh by 62.4 and 61.76 %, respectively comparing with untreated control. While in the 2nd year fusilade at the same micro rate with glue achieved the highest reduction in P. minor fresh and dry weight by 45.6 and 56.3% respectively comparing with the control. The highest reduction in Staria sp. fresh and dry weigh achieved from fusilade at micro rate with mineral oil by 65.31 and 71.18(1styear) and with rape seed oil 54.6 and 56.8% (2ndyear) respectively than its respectable control. There’s no change in seed proteins types and percentage were detected after applying fusilade on broad bean in the presence or absence of biofertilizers. While the dual inoculation proved to be the most effective biofertilizers that increase protein components at the both seasons by (12.8% and 12.04%, respectively). Generally, a positive correlation was found between biofertilizers and fusilade on broad bean yield, so that to maximize broad bean productivity and reducing production costs as well as weed suppression, thus it is recommended for cultivating broad bean with dual inoculation (R. leguminosarum plus B. megaterium) asbiofertilizersand using fusilade at (1.0 L/fed.) with spray tank additives for a narrow weed control which increased productivity of broad bean during the two years ranged from 324.01 to 349.27% (mineral oil) and with 296.06 and 340.32% (glue), respectively, and seed protein than untreated control.

The herbicidal potential of culture filtrates of four Trichoderma spp., namely Trichoderma harzianum Rifai, Trichoderma pseudokoningii Rifai, Trichoderma reesei Simmons and Trichoderma viride Pers., was evaluated against two problematic weeds of wheat, Phalaris minor L. and Rumex dentatus L. In laboratory bioassays, generally, metabolites of all four Trichoderma species significantly reduced various root and shoot growth parameters of the two target weed species. The original concentrations of the culture filtrates of all Trichoderma spp., except T. harzianum, significantly reduced various parameters of root and shoot growth of wheat seedlings. In a foliar spray bioassay, the culture filtrates of all four Trichoderma spp. significantly diminished root and shoot biomass of R. dentatus. The effect of these filtrates on the shoot growth of P. minor and wheat was not significant. Culture filtrates of the four Trichoderma species were successively extracted with butanol, n-hexane, chloroform and ethyl acetate. In detached leaf injection bioassays, n-hexane fractions (3 mg mL(-1)) of T. pseudokoningii, T. reesei and T. viride, and ethyl acetate fractions of T. horzianum and T. pseudokoningii were found to be toxic against R. dentatus. This study concludes that the culture filtrates of Trichoderma species have herbicidal potential in the control of R. dentatus.

Phalaris minor (littleseed canary grass) is a major weed in wheat fields in some parts of Iran. Diclofop-methyl, fenoxaprop-P-ethyl, and clodinafop-propargyl are three acetyl coenzyme A carboxylase (ACCase)-inhibiting herbicides that are commonly used to control this grass in wheat fields.Thirty-four P. minor populations with suspected resistance to ACCase-inhibiting herbicides were sampled from wheat fields in the provinces of Fars and Golestan in Iran.The dose‐response assays that were conducted under controlled greenhouse conditions indicated that 14 populations were resistant to fenoxaprop-P-ethyl, seven populations were resistant to both fenoxaprop-P-ethyl and diclofop-methyl, and three populations were resistant to fenoxaprop-P-ethyl, diclofop-methyl, and clodinafop-propargyl. These populations showed different levels of resistance to the applied herbicides,compared to the susceptible population. These results suggest that different mechanisms of resistance could be involved.The enzyme assay revealed that the existence of modified ACCase in the three most-resistant populations (AR, MR4, and SR3) is responsible for the resistance of these populations.

Wheat (Triticum aestivum L.) production in the warm areas of South Asia is severely affected by spot blotch caused by Cochliobolus sativus. There are several inoculum sources suspected to harbor C. sativus during the off season. This study was conducted to determine survival and potential sources of C. sativus inoculum from rice stubble, wheat seed, soil and weeds in three cropping systems (wheat-rice, wheat-fallow and wheat-green manure) during the 2004 and 2005 wheat growing seasons at Rampur, Nepal. Wheat seed, soil and rice stubble in the field, and weed plants in and around research plots were examined for the presence of the pathogen. Koch’s postulates were applied to verify representative strains. The pathogen was found in the wheat seed at moderate to high levels, but was absent in soil samples and rice stubble collected from the field before wheat was sown after rice. Weeds such as Blumea sp., Dichanthium annulatum, Digitaria ciliaris, Phalaris minor, Saccharum officinarum, Axonopus compressus, Brachiaria mutica, Eleusine coracana, Panicum sp., Paspalum scrobiculatum, Pennisetum purpureum, Setaria italica, Zea mays and Zizania aquatica harbored C. sativus. The C. sativus strains isolated from these weeds infected wheat by producing typical spot blotch symptoms. It is concluded that the weeds prevalent in different cropping sequences and on adjacent uncultivated land can serve as secondary hosts for C. sativus. This study presents important new information that could assist in better understanding spot blotch epidemiology and in developing integrated management strategies for spot blotch of wheat in the warmer growing regions of South Asia.

BACKGROUND: The increasing use of ACCase-inhibiting herbicides has resulted in evolved resistance in key grass weeds infesting cereal cropping systems worldwide. Here, a thorough and systematic approach is proposed to elucidate the basis of resistance to three ACCase herbicides in a Lolium multiflorum Lam. (Italian rye grass) population from the United Kingdom (UK24). RESULTS: Resistance to sethoxydim and pinoxaden was always associated with a dominant D2078G (Alopecurus myosuroides Huds. equivalent) target-site mutation in UK24. Conversely, whole-plant herbicide assays on predetermined ACCase genotypes showed very high levels of resistance to diclofop-methyl for all three wild DD2078 and mutant DG2078 and GG2078 ACCase genotypes from the mixed resistant population UK24. This indicates the presence of other diclofop-methyl-specific resistance mechanism(s) yet to be determined in this population. The D2078G mutation could be detected using an unambiguous DNA-based dCAPS procedure that proved very transferable to A. myosuroides, Avena fatua L., Setaria viridis (L.) Beauv. and Phalaris minor Retz. CONCLUSION: This study provides further understanding of the molecular basis of resistance to ACCase inhibitor herbicides in a Lolium population and a widely applicable PCR-based method for monitoring the D2078G target-site resistance mutation in five major grass weed species. Copyright © 2010 Society of Chemical Industry

Summary Photocontrol of weeds requires a better understanding of the effect of light on seed germination. Therefore, the effect of light intensity and exposure duration was tested on seed germination of two winter annual weeds, Phalaris minor and Poa annua. Photo-sensitised seeds of both species were subjected to four light intensities, including 130, 250, 500 and 1000 lmol m )2 s )1 , each at six exposure durations of 0.1, 1, 10, 100, 1000 and 10 000 s. Light stimulated the germination of both weeds. A modelling approach was used to describe the relationship between light intensity and exposure duration with the germination of weed seeds. A combination of logistic and Gaussian models provided good fits to P. minor percentage germination data, whereas in the case of P. annua, the incorporation of logistic and quadratic models better described the relationships. According to the model, increasing light intensity from 0 (full darkness) to 1000 lmol m )2 s )1 increased the germination of P. minor and P. annua from 28% to 57% and from 0% to 35% respectively. The seed germination of both weed species increased with exposure duration, but declined at duration periods longer than 100 s in P. minor or 1000 s in P. annua. The model predicted a trade-off between light intensity and light duration for both weeds. That is, a high light intensity irradiated for a short time exposure may result in the same percentage germination as one with a low light intensity, but at longer exposure duration.

Optimizing the herbicide dose by the addition of adjuvants is an acceptable way to reduce the risk of side-effects from herbicides. Therefore, to detect a suitable adjuvant for diclofop-methyl, cycloxydim, and clodinafop-propargyl against littleseed canarygrass (Phalaris minor) and wild oat (Avena ludoviciana), six dose-response experiments were conducted. The treatments consisted of diclofop-methyl at 0, 112, 225, 450, 675, and 900 g ai ha⁻¹, cycloxydim at 0, 15, 30, 60, 90, and 120 g ai ha⁻¹, and clodinafop-propargyl at 0, 8, 16, 32, 48, and 64 g ai ha⁻¹ with and without the adjuvants of Frigate, olive oil, and castor oil at 0.2% (v/v) in order to control both littleseed canarygrass and wild oat. Tested herbicides performance was enhanced by all adjuvants against littleseed canarygrass and wild oat. The addition of Frigate and the vegetable oils had the lowest and the highest effect on the performance of all of the herbicides on both littleseed canarygrass and wild oat, respectively, which confirms the solubilizing nature of the cuticular waxes by vegetable oils. A comparison between the two vegetable oils revealed that olive oil exerted a greater control of littleseed canarygrass than did the castor oil. In contrast, castor oil exerted a greater control of wild oat than did the olive oil, which can be related to differences in the leaf surface micromorphology of the weeds.

Photocontrol of weeds requires knowledge about the response of weeds to light and its changes over time. Thus, littleseed canarygrass germination, as an important weed in winter crops, in response to the light environment was evaluated in seeds retrieved from different burial (10, 20, and 40 cm, under irrigated or nonirrigated conditions) or storage (room temperature 25 C and cold 3 C) conditions for 1 yr. Seeds buried in the soil showed a cyclical germination behavior when tested at 20 C, with high germination percentages (68%) occurring in August, October, and December and low percentages (12%) in February and April, with another late germination in June. Germination percentages were mostly higher for seeds incubated in light than in darkness and seeds were more likely to positively respond to light in June than at the other retrieval dates, with differences as great as 60% having been observed under irrigated conditions and at depths of 20 and 40 cm. The most outstanding effect of light as a germination stimulus was observed for seeds stored at room temperature where germination in light was always 20 to 35% higher than that in darkness. The viability of seeds did not change over time in seeds kept at room or cold temperature. However, the proportion of surviving seeds was reduced by 35 to 65% when buried in the soil. Littleseed canarygrass seeds tended to survive more when buried 40 cm deep and the differences between irrigated and nonirrigated conditions were only detectable at 10 cm deep, with higher seed mortalities under irrigated conditions. Information gained in this study would be useful in developing weed control programs for this species.

Weed-crop interaction in the agro-ecosystems is a serious biological concern which hampers production and yield of the crops. Present study conducted to assess growth functional traits of selected weed and crop species under weed-crop interaction experiment that was established in a Latin square matrix model (LSM) in the backside of Department of Botany in a fenced dome. We investigated the ability of little seed canary grass that how it suppresses wheat crop growth at vegetative stage under mono- and mixed culture combinations. Data sampling for selected growth traits (Shoot height, Leaf area and Tiller number) were monitored at different temporal days after seed sowing (30-, 60-, 90- and 120 DAS). Results indicated that at initial stage (30 DAS), wheat exhibited significantly better growth (more leaf area and shoot height than little seed canary grass) under both combinations (Mono- and Mixed culture); however, little seed canary grass (Phalaris minor) suppressed both traits of wheat (leaf area and shoot height) due to interspecific competition. After 30 DAS, however little seed canary grass switched own growth traits in increasing mode therefore shoot height and leaf area were increases till 120 DAS, while, growth traits of wheat crop was significantly suppressed. Since, a linear trend was observed in the growth traits particularly shoot height with respect to days after sowing. Therefore, a significant relationship between growth traits and days was developed under both combinations that evidently indicated impact of little seed canary grass on suppression of wheat crop. In conclusion, wheat crop growth seriously undergo suppression due to little seed canary grass as inter-specific competition at least from initial stages of growth while growth traits of little seed canary grass less affected in competition which may be act as facilitation for weed under weed-crop interactions.

Littleseed canarygrass is a major weed of winter-season crops, although it is most dominant in wheat-growing regions in the Indo-Gangetic Plains of India, Pakistan, Nepal, and Bangladesh. Resistance in this species to photosystem II–inhibiting herbicide isoproturon was first recorded in 1992, and has since spread to several Indian states covering more than a million ha. Genetic studies and resistance characterization from multiple locations indicate independent evolution of resistance due to continuous use of isoproturon and monoculture rice–wheat-cropping system. Isoproturon-resistant biotypes were found cross-resistant to diclofop, but not to chlortoluron, which has the same mode of action as isoproturon. The isoproturon-resistance mechanism is metabolic degradation, mediated by P-450 monooxygenase enzymes. This type of resistance could become serious and lead to the evolution of multiple resistances to herbicides of different modes of action. Adoption of fenoxaprop-P, clodinafop, and sulfosulfuron in i...

Phalaris minor is an anuual grass in North temperate regions. This weed is inhabited in damp soils and swamps of Irano-Turanian phytogeographic region. Anatomical structure of leaf trans-sections, dorsal epidermis and morphological variation of 23 accessions of Phalaris minor from different parts of Iran were studied. Coastal and inter-coastal characters were evaluated and the intra-specific variations were studied. Results indicate a lot of variations in shape and wall thickness of long cells, the number and type of short cell, stomata number per leaf area, shape of silica bodies, guard cells and the presence of different kind of hairs. Also sclerenchyma position, the shape of midrib and furrows of leaf blade and the features of vascular bundles show a lot of variations. Different accessions show variations in shoot length and spike shape and length. The results indicate that there may be some ecotypes in Phalaris minor of Iran. Statistical analysis is provided for Iranian populations of weedy Phalaris minor.

Summary Studies were conducted to investigate seed longevity, seedling emergence and seed production of the weed Phalaris minor in wheat in northern India. The longevity of P. minor seeds buried in bags in the field was often limited to less than 1 year, although many seeds buried at 30 cm depth in a rice–wheat rotation remained viable for longer. The application of direct seeding in wheat reduced the seedling emergence rate of P. minor, when compared with conventional ploughing and sowing. However, a larger P. minor seedbank in the upper soil layer in plots under direct seeding partly reversed this positive effect in one of the two studies. Besides differences in relative distribution of weed seeds through the soil profile, it was likely that other factors such as reduced soil disturbance and soil characteristics associated with the application of direct seeding were also involved in regulating the emergence rate. Mature P. minor plants in wheat were found to invest a stable part (27%) of their aboveground biomass in seed, so that total seed weight was strongly linearly correlated with the aboveground biomass of the mother plant. Individual seed weight, however, was little affected by the weight of the mother plant.

To take full advantage of site-specific variable rate technology (VRT) systems, highly accurate digital mapping of weed infestations within fields via scouting, GPS, GIS and remote sensing technologies will be necessary. When combined, these tools can increase weed control efficiency and reduce herbicide use and residues, thereby avoiding excess applications that lead to increased costs, potential herbicide resistance in the field and runoff into the environment. Keeping this in view, a field experiment was conducted at the Research Farm, Department of Agronomy, Punjab Agricultural University, Ludhiana, Punjab, for 2 years to study the multispectral remote sensing to distinguish the little seed canary grass (Phalaris minor) from wheat crop under field conditions for environmental sustainability and precision weed management. The experimental site during both the seasons were sandy loam in texture, with normal soil reaction and electrical conductivity, low in organic carbon and available nitrogen and medium in available phosphorus and potassium. The experiment consisted of five treatments, viz, T1,, control (weedy check); T2, half of the recommended dose of herbicide for partial control of Phalaris minor; T3, recommended dose of herbicide to obtain economic threshold level to control Phalaris minor; T4, manual weeding (partial), done after a month of sowing of crop; and T5, weed free (manual). The treatments T3 (recommend dose of herbicide) and T5 (weed free, manual) being at par with one another recorded highest plant height, dry matter accumulation and number of tillers per plant by wheat at all observational dates during both the years in experiments, whereas minimum plant height, dry matter accumulation and number of tillers per plant were recorded in control treatment (T1). Reduction in dry matter production, number of tillers as well as effective number of tillers and ultimately yield of wheat are mainly attributed to the reduction in the number of effective tillers, lesser number of grains per spike and lesser 1000-grain weight. The weed-free treatments (T3 and T5) had lower red reflectance percentage as compared to other weed control treatments. The control treatment recorded the highest red reflectance. On the other hand, the two weed-free treatments T3 and T5 had higher IR reflectance percentage as compared to other three weed control treatments, and the lowest IR reflectance was recorded under control treatment. Highest RR and NDVI values were obtained in treatments T3 and T5 where there was no competition between wheat and weeds, and control treatment had the lowest RR value amongst all the treatments during both years. Differences in RR between these three treatments are mainly due to dark green colour of wheat, more leaf area index (LAI) and more biomass of wheat as compared to Phalaris minor. The RR value increases in the early stages of crop growth which is maximum at maximum crop canopy cover and after that decreases as the leaves senesce. The highest RR values were obtained at 95 days after sowing almost in all the treatments. It is feasible to distinguish pure wheat from weeds just 34 days after sowing, but amongst different weed control treatments, i.e. pure Phalaris minor plot and less/partial Phalaris minor weeds 52 days after sowing amongst themselves, and they remain distinguished up to 107 days after sowing based on their NDVI values. After 52 DAS, the differences in the NDVI of different weed control treatments were very clear. So, from such type of information, we can discriminate/define the areas which are heavily or partially infested with weeds so that timely weed control measures can be taken which can help the farmers in preventing yield losses due to weeds.

Unharvested stubbles or harvested straw of rice (Oryza sativa L.) gets incorporated into soil and interferes with the seedling growth of crop plants. In this paper, we investigated whether rice straw, either through releasing allelochemicals and/or through manipulating soil properties, influences seedling growth of Phalaris minor Retz., a non-native weed largely restricted to wheat (Triticum aestivum L.) fields. One hundred twenty grams of soil was amended with rice straw (0.5, 1, 2, 4, or 6 g/pot) and its effect on fresh shoot biomass of P. minor was examined. Any modification of rice straw phytotoxicity through the use of washed rice straw, activated charcoal, soil sterilization, or nitrogen fertilization was also studied. We carried out chemical and microbial analysis of soils to examine the role of soil properties in influencing P. minor growth. Incorporation of rice straw into soil suppressed the growth of P. minor through modifying soil properties. A dose-dependent increase in total phenolics was observed in soil amended with rice straw. Activated carbon or washing of rice straw, however, could not ameliorate the phytotoxic effects of rice straw. Our results provide initial evidence that rice straw restricts P. minor growth by manipulating soil chemical and microbiological properties.

The nutritional worth of Phalaris minor seeds was assessed in comparison to conventional cereal grains like maize and wheat. P. minor seeds had higher total ash and cell wall constituents as compared to wheat and maize grains. The CP content of P. minor was comparable to wheat grains but higher than maize grains. The in vitro studies revealed that the net gas production and availability of ME from P. minor was comparable to that of maize but the digestibility of nutrients was significantly (p

Intra- and inter-sample similarities for four populations of the annual grass weed Phalaris minor from Haryana state, India, were examined using inter-simple sequence repeat (ISSR) DNA markers. Levels of polymorphism within and between populations were low in comparison with values reported from other grassy weed species. Analysis of inter-population similarities allowed a partial differentiation of the four populations and of pairs of populations classified by cropping system. Analysis of the intra-population similarity data showed a weak but consistent and statistically significant negative correlation between the molecular similarity of seedlings and the physical distance between their mother plants over distances up to 40 m (the maximum separation tested) in all four populations. The consistency of the observed relationship between molecular similarity and physical separation, and the differences in cultivation practices at the four sites, suggested that the relationship may be a result of localized out-crossing, rather than an effect of localized seed rain. The results of the analyses are discussed in relation to the potential for evolution of multiple traits in the weed in response to changes in the wheat production system in the region.

Summary Seed placement, soil temperature and soil moisture content influenced the process of after-ripening in Phalaris minor seeds. Seeds of P. minor collected from the soil just after wheat harvesting exhibited higher germination than seeds from P. minor threshed directly. There was a pronounced impact of periodic inhabitation of seed into the soil on germination after its dispersal. Germination was strongly inhibited when the seed was kept in soil at more than field capacity (FC) or in water. Maximum germination of seed incubated in soil at FC occurred at 30°C while a temperature of 40°C favoured after-ripening of seed when mixed with dry soil or kept dry without any medium. Release from conditional dormancy was quicker in the seed retrieved from the soil kept at 20°C than at 10°C. Seed release from conditional dormancy and germination increased with a rise in temperature from 30 to 40°C when the seed was retrieved from incubation in soil at FC for 70 days. The seed kept immersed in water was least responsive to a rise in temperature. Seed recovered from dry soil, or kept without any medium, responded quickly at both temperatures. Light enhanced the germination of Phalaris minor seed. The seedbank subjected to rice (Oryza sativa) field management conditions lost vigour in comparison with the seed stored in laboratory. There was significant variability in seed viability when exposed to differential water management conditions in rice.

Phalaris minor Retz. (Littleseed canarygrass) is a pernicious weed, which infests several crops during the winter season, particularly the wheat crops in rice–wheat sequence. Considering the limitations of cultural and chemical methods of weed control, the understanding of its biology with respect to different environmental, edaphic and management factors may offer a useful key to strengthen weed management strategies. This review considers various aspects on dormancy, viability and agro-ecology with emphasis on management practices in host and succeeding crops. Due attention has been given to the approaches required to manage the resistant biotypes under present conditions and hence to avoid further escalation of the epidemic. The various studies indicate that P. minor utilizes beneficially the prevailing environmental and management conditions of both the wheat and succeeding rice crop in rice–wheat system for its survival and growth. Its seed is highly sensitive to variable moisture and temperature regimes for germination and exhibits tolerance to anoxia during anaerobic respiration in rice. Tillage options, residue management, spatial–temporal considerations and other factors influence the seed dynamics, pattern and depth of emergence and growth of P . minor . A comprehensive and conceptual understanding of these aspects may provide useful guidelines in formulating cautious and opportunistic weed management strategies.

Littleseed canarygrass (Phalaris minor Retz.) is a major weed in wheat fields, and has developed resistance to the commonly used herbicide isoproturon. This study explores the potential use of isoxaflutole, a pre-emergence herbicide, to control littleseed canarygrass. Greenhouse studies were carried out to determine the phytotoxicity of isoxaflutole in relation to shoot height, fresh shoot biomass and leaf chlorophyll concentration of wheat and littleseed canarygrass. Electron microscopy was used to examine any damage to leaf chloroplast at ultrastructural level. Results indicate that isoxaflutole (0.5 mg/L) significantly reduced the shoot height of littleseed canarygrass (39.6%), but no significant reduction in the shoot height of wheat was observed (9.6%) when compared to control. None of the concentrations (0.05, 0.1, 0.5 and 1 mg/L) of isoxaflutole altered soil chemistry in relation to pH, organic matter, macro or micro inorganic ions. While untreated littleseed canarygrass leaves had elongated chloroplast, starch grains and small number of plastoglobuli; treated littleseed canarygrass leaves had swollen chloroplast, large number of plastoglobuli, and a lack of starch grains. We conclude that isoxaflutole can be an effective herbicide for controlling littleseed canarygrass.

Field experiments were conducted in northern Greece during 1994, 1995, and 1996 to study the effect of nitrogen fertilization on competition between littleseed canaryglass (Phalaris minor Retz.) and wheat (Triticum aestivum L.), barley (Hordeum vulgare =distichum L.) or triticale (Triticosecale). The presence of 400P. minor plants per square meter until early March did not have an adverse effect on dry weight of any crop. However, their further presence significantly reduced dry weight of wheat and triticale, but not that of barley. Grain yield of wheat and triticale was reduced 48% and 47%, respectively, by season-long competition ofP. minor, whereas the corresponding reduction for barley was only 8%. Crop yield reduction due toP. minor competition resulted mainly from reduction in ear number and less from reduction in 1000-grain weight. Nitrogen fertilization (150 kg N ha−1), compared with control (0 kg N), slightly increased yield of all crops grown without weed competition. The same treatment also increased dry weight and competitive ability ofP. minor against wheat and triticale, compared with that of control (0 kg N); the split application of nitrogen (50 kg N ha−1 before crop sowing and 100 kg N ha−1 in early March) caused a slightly greater increase inP. minor dry weight than did 150 kg N ha−1 applied once before crop sowing. Dry weight ofP. minor grown with barley was not affected by nitrogen fertilization, but it was severely reduced compared with that ofP. minor grown with wheat or triticale.

Green manuring of sunflower and dhaincha reduced plant population of Phalaris minor 100 per cent under lab and 42 per cent and 15 per cent, respectively, under field conditions, thus, indicating the inhibitory role of allelo-chemicals. Grain yield of wheat was significantly higher with the green manuring of sunflower and dhaincha before rice transplanting over summer fallow. The allelopathic potential of broad-leaved weeds of wheat in inhibiting germination of P. minor was in the order of Chenopodium album=Medicago denticulata=Melilotus indica=Convolvulus arvensis (100 per cent inhibition) > Vicia hirsuta (86 per cent) > Cirsium arvense (48 per cent) > Lathyrus aphaca (38 per cent) > Rumex acetosella (9 per cent). Exudates of rice cultivars HKR 126, IR 64, Jaya and Haryana Basmati-1 registered >50 per cent inhibition of germination of P. minor . As the extract was diluted, effect of non-scented cultivars considerably reduced in comparison to scented group. Out of 11 wheat varieties, WH533 provided the highest inhibition of germination (30 per cent) followed by WH542 (21 per cent).

Littleseed canarygrass, a troublesome wheat weed, has developed resistance against isoproturon in India. Laboratory, pot, and field experiments were conducted to quantify the level of isoproturon resistance in various littleseed canarygrass biotypes and to evaluate the response of isoproturon-resistant littleseed canarygrass to alternate herbicides. For quantification of resistance, 10 littleseed canarygrass biotypes were collected from fields with a varied history of cropping and herbicide use. Pot studies indicated that 6 out of the 10 biotypes tested were resistant to isoproturon. The resistant (R) biotypes had 50% growth reduction values, 5 to 10 times greater than that of the most susceptible biotype. The R biotypes were from areas where isoproturon had been used continuously for more than 10 yr in wheat under a continuous rice–wheat cropping system. The isoproturon resistance was not detected where crops and herbicides were rotated. Under field conditions, postemergence isoproturon at 1,000 g/ha 32 ...